Question

The characteristic length of the SGS eddies is __________

(a) half of the filter cut-off width

(b) the filter cut-off width

(c) twice the filter cut-off width

(d) thrice the filter cut-off width

I got this question during an interview.

Enquiry is from Turbulence Modelling topic in division Turbulence Modelling of Computational Fluid Dynamics

Answer 1

Correct answer is (b) the filter cut-off width

For explanation: The LES filter accepts and rejects eddies based on the filter cut-off width. So, the size of the SGS eddies is determined by the filter cut-off width and the same is used as the characteristic length.